Modelling and Control of Co-Generation Power Plants Under Consideration of Lifetime Consumption: A Hybrid System Approach

Abstract

In this paper the load optimization of a combined cycle power plant under consideration of the real cost of lifetime usage is accomplished by exploiting hybrid systems, i.e., systems evolving according to continuous dynamics, discrete dynamics, and logic rules. The possibility of turning on/off the gas and steam turbines, the operating constraints (minimum up and down times) and the different types of start up of the turbines characterize the hybrid behavior of a combined cycle power plant. In order to model both the continuous/discrete dynamics and the switching between different operating conditions we use the framework of Mixed Logic Dynamical systems. Next, we recast the economic optimization problem as a Model Predictive Control (MPC) problem, that allows us to optimize the plant operations by taking into account the time variability of both prices and electricity/steam demands. Because of the presence of integer variables, the MPC scheme is formulated as a mixed integer linear program that can be solved in an efficient way by using commercial solvers.

Investment analysis of an integrated industrial park with carbon capture

“…Optimisation models of Natural gas power plants are presented in Makkonen andLahdelma (2006), Ferrari-Trecate et al (2002) and Yokoyama and Ito (2006). While Makkonen and Lahdelma (2006) use a non-convex optimisation approach, Ferrari-Trecate et al (2002) and Yokoyama and Ito (2006) linearize the gas turbine operation in the power plant and use a MIP model for their analysis. We also find examples of simulation approaches, for instance in Knight et al (2004) and Attala et al (2001).…”

Tutorial introduction to the modelling and control of hybrid systems

“…Moreover, gas turbine efficiency and emissions performance improves as load increases. The dynamic equations describing the behaviour of the gas turbine at various operating points are based on the models reported in Ferrari-Trecate et al (2002) and Ordys et al (1994). Inputs to the gas turbine are:…”

“…This corresponds to a downtime assumption of 3 hr (normal) or more than 2 hr (cold) shown in Table 1. The several start up modes are modelled introducing continuous state variables x off (t) and x su (t) that define respectively the uninterrupted time during which the turbine is switched off and the duration of the start up procedures (Ferrari-Trecate et al, 2002). The dynamics of these variables is expressed by the relation:…”

Modeling and Control of Co-Generation Power Plants: A Hybrid System Approach

“…In fact, different piecewise affine terms, reflecting other performance criteria could be added without changing the structure of the resulting optimization problem [14]. For instance, asset depreciation due to plant aging can be incorporated by exploiting piecewise linear lifetime consumption models, see [18] and [13] for details.…”